We are given following coordinates in given graphs (1000,12000), (1500, 16000), (500 , 8000) , (2000, 18000).
Let us discribe each given coordinate and cost per square foot area for each coordinate (in each graph).
1st (1000,12000) : represnts 1000 square foot area cost $12000.
Cost per square feet = 12000/1000 = $12.
2nd (1500, 16000) : represnts 1500 square foot area cost $16000.
Cost per square feet = 16000/1500 = $10.67.
3rd (500 , 8000) : represnts 500 square foot area cost $8000.
Cost per square feet = 8000/500 = $16.
4th (2000, 18000) : represnts 2000 square foot area cost $18000.
Cost per square feet = 18000/2000 = $6.
Therefore, 4th graph with (2000, 18000) coordinate shows the lowest cost that is $6 per square foot for a new home.